What role does union with Christ play in being light?

Believers are called to shine as lights in the world only because of their union with Christ. This union ensures that His life, goodness, and light manifest in them. Colossians 1:27 describes this as 'Christ in you, the hope of glory.' When believers are in communion with Christ, they are empowered to reflect His light and goodness in their lives. The understanding of being the light of the world is predicated on recognizing that apart from Christ, we can do nothing (John 15:5). Thus, our effectiveness in shining for Christ directly correlates with our relationship with Him and our reliance on His grace.